To Prepare Batter: Line twelve 2-1/2-inch-diameter muffin pan c. with paper baking c. and set aside.
Preheat oven to 400 F.
In mixing bowl combine first 4 ingredients.
In 2-c. measure or possibly bowl combine lowfat milk, apple, margarine, and egg; pour into dry ingredients and stir till combined (don't beat or possibly overmix; batter should be lumpy).
Fill each baking c. with an equal amount of batter (each will be about 2/3 full).
To Prepare Topping and Bake: In small bowl combine all ingredients for topping, stirring till thoroughly combined; sprinkle an equal amount of topping over each muffin and bake for 15 to 20 min (till muffins are golden and a toothpick, inserted in center, comes out dry).